It is the aim of the proposed research to study the effects on the cardiovascular system and on the actions of certain cardiac drugs of the biphasic changes in plasma (K ion) caused by epinephrine; to determine what organs or tissues accumulate or release potassium to produce the observed changes; to determine the effects of induced sympathetic nervous system activity on plasma (K ion) and the possible role of the hypokalemic effect in the normal control of plasma (K ion); and to characterize the specific adrenergic receptor mechanisms mediating the effects.